1. Field of the Invention
This invention relates to trailers used for receiving, transporting over the road, and discharging lightweight vehicles such as snowmobiles, motorcycles, all terrain vehicles and the like.
2. Description of the Prior Art
The popularity of snowmobiles in the northern tiers of states and in the mountains during the late 1960's and in the 1970's resulted in the development of many varieties of trailers designed to carry these relatively narrow, motor powered, relatively lightweight vehicles from the owner's home bases to areas suitable for their use. The boom in the use of trailers to make possible such recreational activity in the cold climes of the United States, Canada and elsewhere in the world rivals the development and use of special use trailers to carry recreational boats to areas far from home and back again.
Many such snowmobile trailers were developed, some were patented, and many were quite suitable for the usages to which they were put. However, as in any boom of this nature, the relationship of weight, ease of operation, reliability, and usable life to cost was not a critical factor in the early years of the boom.
This activity now continues at a strong and steady rate; but efficiency, weight, reliability, trouble-free operation and useful lifetime in relationship to initial cost and cost of upkeep are now much more important factors.
A snowmobile necessarily uses skis or runners to support its front end and to steer it. It uses a relatively wide continuous track extending from the middle toward the rear to support the rear end and, most importantly, to drive the vehicle forward. Because skis and runners are effective in a forward direction only, it is generally not considered worthwhile to provide for powered drive in a reverse direction. Therefore, snowmobile trailers are often either provided with some way of discharging the snowmobiles in forward direction; or are provided with some means of depositing the rear end and track of the snowmobile on the ground and then pulling the trailer out from under it.
It is known to drive snowmobiles up on tilting trailer beds or platforms which are pivoted to trailer frames and to have those snowmobiles tip forward into horizontal positions as their centers of gravity pass the platform pivot points U.S. Pat. No. 3,786,950 granted to Zemien on Jan. 22, 1974; and U.S. Pat. No. 3,731,831 granted to Huff on May 8, 1973.
It is known to use parallel pairs of individually mounted trailer beds or platforms to receive, transport over the road, and discharge two snowmobiles or the like. See the following U.S. Pat. Nos. 4,168,932 granted to Clark on Sept. 25, 1979; 3,720,336 granted to Murray et al on Mar. 13, 1973; 3,945,521 granted to Decker on Mar. 23, 1976; and 3,604,579 granted to Jenkins on Sept. 14, 1971.
Various structures have been developed to allow snowmobiles to be driven forwardly to discharge them from snowmobile trailers. U.S. Pat. No. 4,014,444, granted to Jakel on Mar. 29, 1977 does not use a pivoted trailer bed, but rather uses a ramp which can be fastened behind a horizontal trailer bed so that a snowmobile can be driven up onto the bed from the rear, and utilizes the same ramp when fastened in front to deflect the skis or runners of the snowmobile to steer it and support it as it moves forwardly under its own power to leave the trailer.
Several of the patents listed above disclose elaborate, expensive and relatively unwieldy turntables between the trailer beds and fixed trailer frames. See U.S. Pat. Nos. 3,720,336; 3,945,521; and 3,604,579.
U.S. Pat. No. 3,731,831, also listed above, shows a trailer with a rigid frame to which is pivoted a drawbar or tongue. This drawbar can be swung under the trailer main frame at 90.degree. either to the right or to the left in order to let a trailer bed pivot toward its front end so that a snowmobile can be driven forwardly off of the trailer.
U.S. Pat. No. 4,051,967, shows a structure whereby the rear end of a snowmobile is supported on an open U-shape subframe or trailer bed which is pivoted to an open U-shape trailer frame. To discharge the snowmobile, the bed is tipped back to allow the snowmobile to rest on the ground, the support between the rear of the snowmobile and the trailer bed is removed, and the trailer is then pulled ahead leaving the snowmobile discharged from it and ready for its intended use.
Also cited during a preliminary search on this invention were the following, which are not considered to be as pertinent as those discussed above: U.S. Pat. Nos. 3,730,542 granted to Chadwick on May 1, 1973; 3,720,335 granted to Ward on Mar. 13, 1973; 3,989,270 granted to Henderson on Nov. 2, 1976; and 4,222,698 granted to Boelter on Sept. 16, 1980.
Neither the inventor nor those in privity with him are aware of any prior art which is closer than that discussed above. Neither are they aware of any prior art which anticipates the claims set out herein.